Polymerization process



United States Patent 3,418,297 POLYMERIZATION PROCESS Lowell D. Grinninger, Harry Greenberg and Virgil L.

Hansley, Cincinnati, Ohio, assignors to National Distillers and Chemical Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed Nov. 14, 1966, Ser. No. 593,718 11 Claims. (Cl. 26082.1)

ABSTRACT OF THE DISCLOSURE A process is provided for control of the molecular weight of alfin polymers and copolymers by carrying out the polymerization in the presence of an alfin catalyst and an alkyl or polyalkyl ether of a dihydrobenzene or a dihydronaphthalene, or mixtures thereof, as a molecular weight modifier.

This invention relates to a process for the controlled polymerization of unsaturated organic compounds and, more particularly, to an improved process for the production of polymers and copolymers of unsaturated organic compounds, said polymers and copolymers having controlled molecular weights. Specifically, the invention provides a new class of compounds capable of functioning as molecular weight control agents in the production of polymer products by polymerizing or copolymerizing unsaturated organic compounds in the presence of an alfin catalyst.

The polymerization of unsaturated organic compounds, e.g., ethylenically unsaturated compounds such as conjugated diolefins including 1,3-butadiene, with or without comonomers such as vinyl aromatics including styrene, in the presence of an alfin catalyst, as defined hereinafter, is known. The use of an alfin polymerization catalyst results in an unusually rapid rate of reaction and in good yields of polymer. In comparison with synthetic rubbers made by conventional catalytic polymerizing techniques, the alfin rubbers are generally gel-free and have higher flex-life values, high tensile strength, superior abrasion resistance and tear strength. Alfin rubbers however, have the disadvantage of being characterized by extremely high molecular Weights, i.e., 5,000,000 and over as indicated by viscosity measurements. Because of such high molecular weights, these rubbers are very tough and exhibit little breakdown and extremely poor banding on being milled. They are, therefore, very difficult to process using conventional equipment and conventional procedures, and attempts to mill and compound them result in very rough stocks with relatively high shrinkage and exceedingly high viscosities. Attempts to obtain an alfin rubber of lower molecular weight by regulating the polymerization have proved unsuccessful, and so, until now, alfin rubbers have been commercially unattractive.

More recently, process modifiers have been discovered which have the cumulative effect of modifying the process of the polymer formation to give molecular weight controlled alfin polymers. Recently issued US. Patent No. 3,067,187 discloses a process for controlling the molecular weights of alfin catalyzed polymers which comprises carrying out the polymerization in the presence of certain dihydro derivatives of aromatic hydrocarbons which include 1,4-dihydrobenzene, 1,4-dihydronaphthalene, 1,2-dihydrobenzene, dihydrotoluene, and dihydroxylene, and the like, and mixtures of these, with 1,4-dihydrobenzene and 1,4-dihydronaphthalene being preferred.

In accordance with the present invention, a new class of compounds has been discovered which is useful for the controlled polymerization of unsaturated organic ICC monomeric materials and mixtures of unsaturated organic monomeric materials either with or Without other organic compounds copolymerizable therewith, with an alfin catalyst.

Specifically, it has been discovered that an elastomer having controlled molecular weight can be prepared by polymerizing an unsaturated organic compound, such as 1,3-butadiene, or a mixture of an unsaturated organic compound and an organic compound copolymerizable therewith, such as styrene, using an alfin catalyst where the polymerization is carried out in the presence of a suitable molecular Weight control agent comprising mono or polyalkyl ethers of dihydrobenzenes or dihydronaphthalenes as described more fully hereinafter. The addition of controlled quantities of such a molecular weight control agent to solutions of an unsaturated organic compound such as 1,3-butadiene containing an alfin catalyst gives molecular weights controlled to about 2,000,000 or less, for example controlled molecular weights as low as 50,000 or lower may be obtained. The polymer products so produced have lower intrinsic viscosities than do those made with alfin catalysts but without the use of such molecular weight control agents. The use of such molecular weight control agents does not change the ratio of 1,4-trans to 1,2-isomers in the resultant polymers, the ratio in the range of 2 to 3 in normal alfin rubbers being retained.

Any mono or polyalkyl ether of a dihydrobenzene or a dihydronaphthalene which does not contain a substituent which would destroy the activity of the alfin catalyst may be used as a molecular weight control agent in accordance with the present invention.

Examples of monoor polyalkyl ethers of dihydrobenzenes or dihydronaphthalenes useful in the present invention include but are not limited to methoxy-1,4- dihydrobenzenes, ethoxy 1,4 dihydrobenzenes, butoxy- 1,4-dihydrobenzenes, hexoxy-1,2-dihydrobenzenes, decyl dihydrophenyl ethers, methoxy-1,4-dihydronaphthalenes, methoxy 1,2 dihydronaphthalenes, ethoxy-1,2-dihydronaphthalenes, ethoxy 1,4 dihydronaphthalenes and the like.

Mixtures of the various alkyl ether compounds can also be employed. The compounds 1,4-dihydroanisol and 1,4- dihydrophenetole have been found to be particularly useful in accordance with the process of the present invention.

The amount of molecular Weight control agent needed for any particular level of molecular weight control is in inverse proportion to its level of activity. Also the amount of molecular weight control agent required for a given polymer molecular weight is dependent upon such factors as the temperature and pressure of the reaction and the quantity and type of diluents employed. In general, the amount of the agent used may vary from about one to about eighty percent, based on the weight of polymerizable monomer, with the use of about 1.5 to about 6 percent being most common.

In the practice of one embodiment of the present invention, the reactor is dried, flushed, and blanketed with an inert gas such as nitrogen or argon, and a dry inert hydrocarbon diluent and the molecular weight control agent are introduced. The reactor is then cooled to about 5 to 20 C., preferably to l0 C., the flow of inert gas is diverted, and dry monomer or mixture of monomer and comonomer is condensed into the diluent. Alfin catalyst is then charged into the cold diluent-monomer mixture; the reactor is sealed and shaken vigorously. After about two hours the catalyst is destroyed with ethanol and the polymer is withdrawn. It is then washed with an alcohol, such as methanol or ethanol, to remove 3 the diluent and with water to remove soluble inorganic salt residues; and dried.

In another embodiment of this invention all of the ingredients except the monomer, that is, the diluent, alfin gen or argon, the alfin catalyst appears to be stalbe almost indefinitely.

The polymerization or copolymerization reaction generally takes place at atmospheric pressure and room temcatalyst, and the molecular weight control agent, are in- 5 perature in a suitable selected reaction medium. The prestroduced into the reactor. A controlled flow of monomer sure and temperature conditions, however, are not critiis then fed into the system over a period of about five cal, the reaction occurring at any pressure between about hours. This system. results in greater utilization of the 1 atmosphere and about 50 atmospheres and at any molecular weight control agent than the former system, temperature between about 25 and 60 C. or higher. i.c. because of the extended time of reaction, less molec- The reaction medium is suitably an inert hydrocarbon, ular weight control agent is required to produce a polyexamples including pentane, hexane, a 1:1 mixture of mer of a given molecular weight. hexane and pentane, cyclohexane, decalin, heptane, Where removal of water-soluble residues is not debranched chain saturated hydrocarbons and the like, or sired, the catalyst can be neutralized, e.g., with acetic mixtures thereof, with hexane and pentane being preacid or hydrochloric acid, and the diluent removed by ferred. The rigorous exclusion of water from solvents, distillation while stirring. If desired, before diluent remonomer, and apparatus is essential. moval the polymer may be compounded with any or The process may be conducted in a batchwise, semiall of the conventional vulcanziation or other additives, continuous or continuous manner, and the polymers and such as carbon, zinc oxide, stearic acid, an accelerator, copolymers so produced may be recovered by any of and sulfur, so that the product obtained after diluent re- 0 the conventional techniques. moval represents a completed formulation ready for vul- The more detailed practice of the invention is illuscanization, thus bypassing the usual milling and mixing trated by the following examples wherein parts are given steps. by weight unless otherwise specified. These examples and The process of this invention is particularly well adapted embodiments are illustrative only, and the invention is not to the polymerization of butadiene itself, i.e., 1,3-butaintended to be limited thereto except as indicated by the diene, and to the copolymerization of 1,3-butadiene and appended claims. The alfin catalyst used in these examples styrene or isoprene and will be particularly discussed was prepared in accordance with the procedure described with reference to such homopolymers and copolymers. in U.S. Application Ser. No. 271,487, filed Apr. 8, 1963, The process, however, is also applicable to the formation now Patent No. 3,317,437. of polymers and copolymers of other unsaturated organic Exam 1 p e 1 compounds. The monomeric material polymerized 1n accordance with the process of this invention may include, In Carrying out each experiment, to 105 grams of y for example, butadienes, such as 2,3-dimethyl-1,3-butacommercial hexane diluent was added the amount of diene, isoprene, piperylene, 3-furyl-l,3-butadiene, 3-me- Lihihydroenisoie 1,4-dihldToPhehetoie m thoxy-1,3-.butadiene, and the like; aryl olefins such as Shown) in Table I together with 30 of y styrene, various alkyl styrenes, p-methoxystyrene, alp-hadiehe (about 999% P Y)- ThiS addition was accommethylstyrene, vinylnaphthalene, divinylbenzene and siml- Piished y Cooling the Polymerization bottle Containing lar derivatives, and the like; homopolymers, copolymers, the 105 gthsheXahe to about and Condensing and te polymers repared from any 0115 or any combin therein the gms. of 1,3-butadiene. catalyst, 4 ation of the above are contemplated to be within the scope aiiyisodillm/ was added to the f the process f hi invention, butadiene-hexane solution. The polymerization system was The polymerization or copolymerization of these sealed and maintained at room temperature with interactants takes place in the presence of an alfin catalyst mittehtshakihg- After about two hours it was opened and such as that described in US. Patent 3,067,187, i.e., an ethanol was added to destroy the Catalyst and P P intimate mixture of sodium isopropoxide, allyl sodium and tate the p The Polymer Product was washed intersodium chloride. In general, the alfin catalyst is prepared mittehtiy with ethanol and water, Containing ahtioXidaht by reacting amyl chloride and sodium in pentan i h to remove diluent and soluble inorganic residues such as high-speed stirring. One mole of the resulting amyl sodi Sodium iSoPToP'oXide and Sodium chiol'ide- The resulting um suspension is then reacted i h 5 mole f isopropyl insoluble material was a White solid polybutadiene. It alcohol and an excess of propylene to give a mixture conwas given a final wash with acetone containing all antitaining sodium isopropoxide, allyl sodium, and sodium oxidant, -P Y P and then dried in an chloride. A particularly effective alfin catalyst is obtained oven at under Veehuih- Yields, ihtl'ihsie viscosities when the sodium is employed as a fi l divided and molecular weights are reported in Table I. Average persion, that is, a dispersion in which the average particle molecular weights were determined by Preparing and size is about-1 to 2 microns, such as may h prepared 1.0 percent solutions of the polymers in toluene, determinusing a Mantoh Gauhn m w such fi l di ing their viscosities at 25 C. and extrapolating the vissodium is used, ordinary stirring devices may be emeosity to infinite dilution, and then pp y Standard ployed instead of high-speed comminuting equipment. In Viscosity-molecular weight iawsaddition, the use of finely divided sodium results in a Moieeuiaf weights were Calculated Using substantially quantitative yield of amylsodium and, therethe expression fore, in subsequent quantitative yields of sodium ison propoxide and allylsodium. Thus the alfin catalyst and Ill consequently the end products of the polymerization are k free of metallic sodium contamination. Also catalyst 20- where n is the intrinsic viscosity and k and a are contivity can be more readily reproduced when finely divided stants for polybutadiene determined for linear polymers sodium (about 2 micron average particle size) is used. of known molecular weights; a is taken as 0.62 and k When maintained under an inert atmosphere, e.g., nitro as 11 l0 TABLE I Agent, Polymer, Intrinsic Calculated Expt. No. Control agent gins/30 g. yield viscosity mol.

butadiene 1 1,4-dihydr0anisole 4.0 69.2 2.76 302, 000 2 lA-dihydrophenetolen 4.0 59.6 5. 63 924, 700

What is claimed is:

1. In a process for preparing a polymer from at least one unsaturated organic monomer by polymerization of said monomer in the presence of an alfin catalyst, the improvement which comprises carrying out said polymerization in the presence of a molecular weight control agent comprising a monoalkyl ether of a dihydrobenzene, a polyalkyl ether of a dihydrobcnzene, a monoalkyl ether of a dihydronaphthalene, a polyalkyl ether of a dihydronaphthalene or mixtures thereof.

2. The process of claim 1 in which the polymer is a homopolymer.

3. The process of claim 2 in which the polymer is polybutadiene.

4. The process of claim 1 in which the polymer is a copolymer containing a conjugated diolefin.

5. The process of claim 4 in which the polymer is a copolymer of 1,3-.butadiene.

6. The process of claim 4 in which the polymer is a copolymer of 1,3-butadiene and styrene.

7. The process of claim 1 in which the polymer is a terpolymer.

8. The process of claim 1 in which said molecular References Cited UNITED STATES PATENTS 2,008,491 7/1935 Ebert 2606 3,067,187 12/ 1962 Greenberg et al. 260942 3,223,691 12/1965 Greenberg et al. 26093.5

JOSEPH L. SHOFER, Primary Examiner.

J. C. HAIGHT, Assistant Examiner.

US. Cl. X.R. 

